Improvements in the specificity of agents used to treat various disease states such as cancer, metabolic, and inflammatory diseases is of considerable interest because of the therapeutic benefits which would be realized if the side effects associated with the administration of these agents could be reduced. Traditionally, dramatic improvements in the treatment of cancer are associated with identification of therapeutic agents acting through novel mechanisms.
Phosphatidylinositol 3-kinase (PI3K) is composed of a 110 kDa catalytic subunit (encoded by the PIK3CA gene) and an 85 kDa regulatory subunit. The catalytic subunit uses ATP to phosphorylate PtdIns, PtdIns4P, and PtdIns(4,5)P2 to create the second messengers PtdIns3P, PtdIns(3,4)P2, and PtdIns(3,4,5)P3 (PIP3). PTEN, a tumor suppressor which inhibits cell growth through multiple mechanisms, can dephosphorylate PIP3, the major product of PIK3CA. PIP3, in turn, is required for translocation of protein kinase B (AKT1, PKB) to the cell membrane, where it is phosphorylated and activated by upstream kinases. The effect of PTEN on cell death is mediated through the PIK3CA/AKT1 pathway.
PI3Kα has been implicated in the control of cytoskeletal reorganization, apoptosis, vesicular trafficking, proliferation, and differentiation processes. Increased copy number and expression of PIK3CA or activating mutations in PIK3CA are associated with a number of malignancies such as ovarian cancer (Campbell et al., Cancer Res 2004, 64, 7678-7681; Levine et al., Clin Cancer Res 2005, 11, 2875-2878; Wang et al., Hum Mutat 2005, 25, 322; Lee et al., Gynecol Oncol 2005, 97, 26-34), cervical cancer, breast cancer (Bachman, et al. Cancer Biol Ther 2004, 3, 772-775; Levine, et al., supra; Li et al., Breast Cancer Res Treat 2006, 96, 91-95; Saal et al., Cancer Res 2005, 65, 2554-2559; Samuels and Velculescu, Cell Cycle 2004, 3, 1221-1224), colorectal cancer (Samuels, et al. Science 2004, 304, 554; Velho et al. Eur J Cancer 2005, 41, 1649-1654), endometrial cancer (Oda et al. Cancer Res. 2005, 65, 10669-10673), gastric carcinomas (Byun et al., Int J Cancer 2003, 104, 318-327; Li et al., supra; Velho et al., supra; Lee et al., Oncogene 2005, 24, 1477-1480), hepatocellular carcinoma (Lee et al., id.), small and non-small cell lung cancer (Tang et al., Lung Cancer 2006, 51, 181-191; Massion et al., Am J Respir Crit. Care Med 2004, 170, 1088-1094), thyroid carcinoma (Wu et al., J Clin Endocrinol Metab 2005, 90, 4688-4693), acute myelogenous leukemia (AML) (Sujobert et al., Blood 1997, 106, 1063-1066), chronic myelogenous leukemia (CML) (Hickey and Cotter J Biol Chem 2006, 281, 2441-2450), and glioblastomas (Hartmann et al. Acta Neuropathol (Berl) 2005, 109, 639-642; Samuels et al., supra). In view of the important role of PI3K-α in biological processes and disease states, inhibitors and/or modulators of this lipid kinase are desirable.
In addition, combining treatments with different mechanisms of action may lead to enhanced anti-tumor activity as compared to single treatments administered alone. For example, activation of the PI3K pathway may contribute to the resistance of human tumor cells to certain chemotherapeutic agents, such as microtubule stabilizing agents like taxol (Brognard, J., et. al. Cancer Res 2001, 61, 3986-3997; Clark, A. S., et. al. Mol Cancer Ther 2002, 1, 707-717; Kraus, A. C., et. al. Oncogene 2002, 21, 8683-8695; Krystal, G. W., et. al. Mol Cancer Ther 2002, 1, 913-922; and Yuan, Z. Q., et. al. J Biol Chem 2003, 278, 23432-23440).
Accordingly, treatments that combine an inhibitor of PI3K-α with other agents are desirable and needed.